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What is TPMS (Tire Pressure Monitoring System)? How does it function?

WRITTEN BY CHUCK HUANG

 

TPMS stands for Tire-Pressure Monitoring System. It’s an electronic system, which is designed to monitor air pressure inside the tires and report real-time tire pressure information to the driver either via a gauge or a simple low-pressure warning icon. The goal of TPMS is to avoid traffic accidents caused by abnormal tire pressure, extend tire lifetime, reduce poor fuel efficiency and decrease additional tire wear caused by underinflated conditions.

 

The electronic systems can be divided into two types:

  • Indirect TPMS

An indirect TPMS typically detects a low tire by comparing relative wheel speeds via anti-lock brake (ABS) system. It does not have air pressure sensors installed inside the tires and does not use “PSI” to refer calculation of tire pressure. The disadvantage of indirect TPMS is that it actually measures tire rotation speed and often fails to offer accurate data.

 

  • Direct TPMS

Direct TPMS refers to the use of a pressure sensor directly mounted either inside or outside of the tire which could also be further divided into external and internal one. Tire pressure can be individually detected by each wheel and reported into dashboard instrument panel or a corresponding monitor. Comparing with indirect TPMS, direct TPMS uses RF (radio frequency) technology through frequency either 434 MHz or 315 MHz, and can relatively provide accurate data as well as display real-time tire pressures at each location monitored.

 

External
External systems which refer to the sensors that are installed outside of the rim. These are less expensive, easier to install, maintain and use. 

 

Internal
Internal systems refer to the sensors that are located inside of the tire. It is strapped around the wheel or installed by replacing the valve stem. Internal sensor systems require additional antennas in order to receive reliable sensor signals. Although it’s expensive to install and difficult to maintain (often need a technician to operate with a special electronic tool), it’s with longer lifetime, more accurate and even more reliable.

 

How to know if your vehicle is equipped with TPMS system?

There are several different methods to determine whether a particular car is equipped with a TPMS system or not. The easiest way is to check owner’s manual which includes all the information and features on it. If owner’s manual is somehow not accessible, you can check the particular symbol on dashboard upon startup of the car.

 

What to do when your TPMS light turns on?

If the TPMS light illuminates, it indicates your tire pressure is underinflated. First thing to do is check tire pressure with a gauge and inflate any tire that is under low pressure. According to original equipment vehicle manufacturer, the recommended tire pressure is either shown on driver’s door jamb or written on owner’s manual. If the indicator light does not go off when tires have been properly inflated, please visit your local garage to diagnose the problem and perform further system test.

 

How to fit TPMS sensors?

Our Universal and Direct-Fit Sensors are fitted in exactly the same way. They are easy to fit and follow exactly the same process as OE. Follow the 6 simple steps:

 

Step 1

Release air from the tire by removing the valve. Place the wheel on the tire changing machine and break both beads. Ensure the sensor is on the opposite side of the breaking bead.

 

Step 2

Place the wheel on the turntable and demount the tire. The sensor can then be removed.

 

Step 3

Once sensor is removed clear stem hole of any dirt. Remove washer, nut and cap from the new sensor. Install new sensor through the rim hole. Insert the stem then place washer, followed by the nut, back on the valve. Tighten the nut to 4Nm.

 

Step 4

Locate the sensor body on to the other end of the valve stem. Hand-tighten to secure and then tighten the connecting screw to 2.2 Nm.

 

Step 5

Reinstall the tire, making sure no contact is made with the new sensor to prevent damage. The tire, complete with TPMS sensor, is now ready for inflation to the correct PSI level.

 

Step 6

Finally, follow the manufacturer’s standard re-learn procedure. (check vehicle handbook)

 

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